In the field of disk rotor for brake systems, transition of rotor materials from cast iron to light metals such as aluminum has been accelerated in view of reducing the weight of the disc rotor. Research and development relating to the use of metal-based composite materials i.e., Metal Matrix Composite (MMC) including a matrix of aluminum or its alloy and a preform in order to compensate for the insufficient strength and wear-resistance of only aluminum has been actively conducted. A process for manufacturing an aluminum MMC rotor comprising the steps of supporting a porous preform in position in a cavity of a die, and impregnating the preform with molten aluminum which is cast into the cavity in accordance with a pressurizing cast method for conducting die casting has been known. This type of manufacturing process has an important technical object how the preform is stably supported within the cavity.
In a process for manufacturing a fiber reinforced metal member of, for example, Patent Document 1, a portion of molded fiber article (a kind of a porous preform) which is fitted (or set) on a core or die is made so that the fitted portion has a fiber density lower than that of the other portion. By adapting the low density portion of the molded fiber article to the core or the die while it is compacted, the fiber density of the molded fiber article is unified over the entire thereof on setting of the article to the core or die and the molded fiber article in interest is held in a desired position in the casting cavity by a biasing force generated by an elastic action caused on compaction for suppressing the shift of the position of the molded fiber article due to pressurizing casting of a molten metal.
Patent Document 2 discloses that an apparatus for manufacturing a disc rotor wherein a molten metal is poured into a cavity and pressurized while supporting and fixing a preform in the cavity formed by a lower die and an upper die which are provided movable toward and away each other. The apparatus comprises a movable core assembly made up of a plurality of divided core segments which are disposed in an annular manner and are movable in a radial direction, the movable core assembly selectively assuming either one of open and closed states, in an open state the plurality of the core segments being movable in an outer radial direction to allow the preform to be introduced into said cavity, and, in a closed state the plurality of the core segments being movable in an inner radial direction to form a preform supporting portion for supporting the outer periphery of at least one preform.
[Patent Document 1]
Japanese Patent Kokai Publication No. 01-272725 (pages 1 and 2)
[Patent Document 2]
Japanese Patent Kokai Publication No. 2003-139172 (claim 6)